Novel Approaches for Robotic Control Using Flex Sensor

Sangeetha.P et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 5, Issue 2, ( Part -2) February 2015, pp.79-81
www.ijera.com 79 | P a g e
Novel Approaches for Robotic Control Using Flex Sensor
Sangeetha.P*, Deepika R**, Chethana Gosal S***
*Department of E&C, KNS Institute of Technology, Bangalore, India
**Department of E&C, KNS Institute of Technology, Bangalore, India
***Department of E&C, CiTech Bangalore, India
Abstract
The aim of the project is to develop the Prosthetic robotic hand using flex sensor for amputees. The main aim of
the project is to develop the robotic hand that performs pick and place activities. Here we are using flex sensors
to sense the signals from artificial hand signal is transmitted and that signal is used to drive the mechanical
hand. Stroke is the third leading cause of the death. Nearly 7, 00,000 people suffered from stroke last year and
2/3 rd of them survived but were left with many number of disabilities; one such disability is upper extremity
hemiplegia. If the hand and the arm do not have therapy immediately after stroke, it will lose its power and
muscle control, resulting in a claw like appearance and loss of function. Activities of the patient, daily living
activities will be significantly affected.Prosthetic hand must resemble human hand in size and shape and must
perform like human hand.
I. Introduction
The task proposed in this project is to design an
intelligent prosthetic hand. An intelligent prosthetic
hand is defined as „a hand that mimics the natural
movements of the human hand.‟ In order to
appropriately mimic the motion of the human hand,
we must study its natural motions. For instance, the
distal phalanx (finger tip) must rotate about its joint
as the middle phalanx rotates. It is very difficult and
unnatural to bend the finger at the proximal joint,
while keeping the distal joint stiff. The motions of
these two joints are linked and must move together.
On the other hand, the knuckle joint is not linked to
any other joints. The knuckle is able to move the
entire finger with no motion in the proximal or distal
joints. This means that the finger can remain straight
while bending at the knuckle. The thumb is a very
different digit. It only has a knuckle joint and a
proximal joint. These joints in the thumb are unlinked
and can move independently of each other. Once the
natural motions on the human hand are defined, the
design of a prosthetic that can imitate them can
occur. In the design of this prosthetic, space is a very
important constraint. The size of the prosthetic must
also resemble that of the average human hand. This
means that there is not much space to fit actuators
and motors. The fingers themselves are very small
and there will not be any room for actuators that are
powerful enough to accomplish everyday tasks. This
must be accounted for in the prosthetics design. Some
areas where actuators may be placed are in the body
of the hand or in the forearm of a full arm prosthetic.
The scope of this project allows for placement of
actuators and motors in the forearm since the hand is
being designed for a full arm
prosthetic. With preliminary research such as stated
above, concepts for the design can be developed to fit
the criteria.
II. Design
The first step taken when designing the
prosthetic hand was to decide on the best control
mechanism for finger movement. The goal for the
design was to minimize the number of actuators
necessary to control the movement of the finger and
simplify the equations needed to describe the motion
of the finger. There are very many ways to do this
and we explored as many options as possible. There
were several preliminary designs we dealt with
before choosing it was the best approach. The first
proposal, which was the tension controlled model,
consisted of the three joints of the finger, with a cable
attached to a fixed point on each link of the finger
which was run back through the finger to an actuator
mechanism at the hand or behind the wrist.
Figure 1.1 Multiple Tension Cable Design Proposal
Figure1.2 Single Tension Cable Design Proposal
There were two main approaches to this design.
The first, as shown in Figure 1.1 consisted of cables
run over the joints between each link of the finger,
RESEARCH ARTICLE OPEN ACCESS

which would pull the links upwards when tension
was applied to each cable. For this model, each joint
would have a compliant mechanism which forced the
resting state of the links to be in the bent position.
The second approach for this design has the
complaint mechanisms such that the resting state for
the links is in the straightened positions systems to
drive the. In this proposal small tubes could be used
to fill with either air or liquid to actuate the finger.
This proposal was eliminated early on in our design
process due to the noise inherent with pneumatic
systems. The noise would create the same discomfort
life-like prosthetics. The third proposal for the finger
design was a pulley system to control each joint
independently. Pulley‟s would be placed at each joint
in the finger, and would be independently controlled
by its own wire. Fig shows two approaches to this
method. In the second figure, the finger uses
compliant devices to keep the finger straightened at
rest. Therefore, when the actuator is active, the
fingers will bend and hold their positions. When the
actuator becomes inactive, the compliant mechanism
would return the fingers to their straightened
positions. This eliminates the need for two actuators
per joint, and is thus preferable to the method shown
in Figure, which requires one actuator to bend the
finger downwards, and a second actuator to return
the finger to the straightened position.
III. Implementation
Based in the basic design a hand model is
created, it is controlled using a Data Glove on which
the flex sensors are mounted and the mechanical
hand is controlled wirelessly using RF transmitter
and Receiver which is driven by Microcontroller.
Depending on the bend of the flex sensors the hand is
controller and it is using to pick up objects
IV. Result
The different positions of the flex sensors their
digital values are given to the controller and motion
of the motors either in clockwise or anticlockwise
direction makes the hand to grasp and pick up things.
V. Conclusion
A step-by-step approach in designing the
microcontroller based system for measurement and
control of the parameters has been followed. The
results obtained from the measurement have shown
that the system performance is quite reliable and
accurate. The hand glove, which is used to control the
robotic hand is normal glove fitted with flex sensors
along the length of each finger .The flex sensors
output a stream of data that varies with degree of
bend, the output from the flex sensor is analog
values, it is converted to digital and processed by
using arm processor and then it will be used to
control the device. Further improvements will be
made as less expensive and more reliable sensors are
developed for use in agricultural production. This
project is merely a demonstration of what we can do
with if Microcontroller and wireless communication
technology in unison.
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